The vehicle exterior parts, for example, door mirrors, pillars, bumpers, front grilles, cowls and the like, have a high impact resistance and good appearance. With respect to the material, a paint treatment is conducted to the molded article of a thermoplastic resin such as ABS resin, ASA resin, polymethyl methacrylate, polycarbonate, and the like, in order to obtain high quality appearance.
In recent years, the environmental burden is large, the processes are complicated, and failure rate is high, so a paint treatment of the molded article may be omitted by blending a coloring agent in advance in a thermoplastic resin.
When the paint treatment is omitted, because the high weather resistance on a thermoplastic resin is required, AES resin and ASA resin having a good weather resistance has been used, in which ethylene.propylene.non-conjugated diene copolymer, acrylic ester-based rubber, hydrogenated rubber such as hydrogenated butadiene-based rubber, or silicone-based rubber is used as the rubber having a good weather resistance.
However, while manufacturing the molded article, processing the molded article or using the molded article for long periods, in the case where the surface of the molded article is scratched, the design property is seriously deteriorated. And therefore, improvement of scratch resistance is desired in some applications.
In order to improve the scratch resistance of the molded article, a method in which the surface of the molded article is harden by reducing the amount of rubber (see Patent Document 1), a method in which lubricant property of the surface of the molded article is improved by adding a lubricant such as silicone oil, olefin wax and the like (see Patent Document 2), a method in which a layered clay mineral having an organic compound intercalated is added to the rubber-modified thermoplastic resin (see Patent Document 3), and a method in which a specific amount of methyl methacrylate-methyl acrylate-copolymer containing methyl acrylate in a specific range is added to ABS resin (see Patent Document 4) have been proposed.
However, in the method of reducing the amount of rubber as described in Patent Document 1, since the surface hardness of the molded product is increased, scratch resistance is improved against scratches, but impact strength is reduced. There is a limitation to achieve both properties, that is, impact resistance and scratch resistance. In a method of adding a lubricant such as silicone oil and olefin wax as described in Patent Document 2, lubricant properties of the surface of the molded article is improved, but improvement of scratch resistance is insufficient.
Further, breed-out of additives such as silicone oil from the surface of the molded article occurs, and as a result, glossiness and coloration are likely to be deteriorated.
In the method of adding special additives to a thermoplastic resin as described in Patent Document 3, the compatibility with the thermoplastic resin may become insufficient, and appearance such as glossiness and coloration may be deteriorated and, deterioration of impact resistance may occur.
In the method of blending a special resin in ABS resin as described in Patent Document 4, it is possible to obtain the improvement effect of scratch resistance against scratches caused when the surface of the molded article is scratched by a hard substance such as nails. However, scratch resistance against scratches caused when the surface of the molded article is rubbed by the soft substance such as gloves, gauze, and cloth is insufficient.
In addition, the thermoplastic resin is also required to have excellent fluidity during molding, the techniques described in Patent Documents are not insufficient.
By improving the impact resistance of the molded product, not only applications of the molded article applications can be expanded, but also industrial utilities can be expanded, for example, reduced thickness and increased size of the molded article can be realized. Therefore, for improving the impact resistance of the molded article, various methods have been proposed.
In these methods, a method of using a resin material which is a combination of a rubber polymer and a hard resin, so as to increase the impact resistance of the molded article while retaining the characteristics derived from a hard resin has already been employed in industrial production. As such a resin material, an acrylonitrile-butadiene-styrene (ABS) resin, acrylonitrile-styrene-acrylate ester (ASA) resin, an acrylonitrile-ethylene.propylene.non-conjugated diene copolymer-styrene (AES) resin, or thermoplastic resin composition in which a hard resin are further added to these resins, and the like can be mentioned.
Also, when high design properties is desired to the molded product, a coating treatment is conducted to the molded article obtained from these resin materials to obtain a high quality appearance. However, the coating treatment has problems in that the environmental burden is large, the process is complicated, the failure rate is high and the like. Therefore, by blending a colorant to the resin material in advance, the coating process of the molded article may be omitted. Since the high weather resistance in the molded article is required to omit the painting process, the resin material capable of providing a molded article having a good weather resistance, such as AES resin or ASA resin has been used, in which ethylene.propylene.non-conjugated diene, acrylic ester-based rubber, hydrogenated rubber (hydrogenated butadiene rubber), silicone rubber, or the like is used as a rubber polymer.
However, with respect to a molded article using a resin material capable of providing a molded article having a good weather resistance and omitting the coating process, in the case where the surface of the molded article is scratched during the manufacturing the molded article, processing the molded article or using the molded article for long periods, the design property is seriously deteriorated. Therefore, improvement of scratch resistance is desired depending on the molded article applications. Therefore, in order to improve the scratch resistance of the molded article, to use a thermoplastic resin composition described below has been proposed.
(1) a thermoplastic resin composition containing: a graft copolymer obtainable by polymerization of a vinyl-based monomer mixture containing an aromatic vinyl compound and vinyl cyanide compound in the presence of a rubber polymer; and a hard resin, in which the amount of rubber polymer is reduced; the thermoplastic resin composition is used to harden the surface of the molded article (see Patent Document 1).
(2) a thermoplastic resin composition containing: a graft copolymer obtainable by polymerization of a vinyl-based monomer mixture containing an aromatic vinyl compound and vinyl cyanide compound in the presence of a rubber polymer; and a lubricant (polyolefin-based wax, silicone oil); the thermoplastic resin is used to improve the lubricant property of the surface of the molded article (see Patent Document 2).
(3) a thermoplastic resin composition containing: a graft copolymer obtainable by polymerization of a vinyl-based monomer mixture containing an aromatic vinyl compound and vinyl cyanide compound in the presence of a rubber polymer; and a layered clay mineral in which an organic compound has been intercalated (see Patent Document 3).
(4) a thermoplastic resin composition containing: a graft copolymer obtainable by polymerization of a vinyl-based monomer mixture containing an aromatic vinyl compound and vinyl cyanide compound in the presence of a rubber polymer; a copolymer obtainable by polymerization of a vinyl-based monomer mixture containing an aromatic vinyl compound and a vinyl cyanide compound; and a copolymer obtainable by copolymerizing methyl methacrylate and methyl acrylate, in a specific ratio (see Patent Document 4).
When using the thermoplastic resin composition of (1) as above, although the scratch resistance is improved against scratches due to enhancing hardness of the surface of the molded article, impact resistance of the molded article is deteriorated due to the low amount of the rubber polymer. Therefore, there is a limitation in order to satisfy both of impact resistance and scratch resistance of the molded article.
When using a thermoplastic resin composition of (2) as above, although the lubricant property of the surface of the molded article is improved, the improvement of scratch resistance is insufficient. In addition, since the lubricant bleeds out on the surface of the molded article, glossiness and coloration are likely to be impaired.
In the thermoplastic resin composition of (3) as above, the compatibility between the graft copolymer and a layered clay mineral in which an organic compound has been intercalated is likely to be insufficient. Therefore, deterioration in impact resistance and deterioration in appearance (deterioration of glossiness and coloration) are likely to occur.
When using a thermoplastic resin composition of (4) as above, although scratch resistance of a molded article against scratches is improved, abrasion resistance of the molded article against abrasion is insufficient.
In addition, the thermoplastic resin composition is also required to have excellent fluidity during molding, the fluidity of the thermoplastic resin compositions of (1) to (4) is not satisfactory level.
As a thermoplastic resin composition capable of providing a molded article in which impact resistance is improved while retaining the properties derived from the hard resin, the following thermoplastic resin compositions are known.
(1) a thermoplastic resin obtainable by adding AES resin to a hard resin, and in the composition, the amount of the rubber polymer is reduced in order to harden the surface of the molded article (Patent Document 1).
(2) a thermoplastic resin obtainable by adding AES resin to methacrylic ester resin as a hard resin (Patent Document 5).
(3) a thermoplastic resin obtainable by adding AES resin to maleimide-based copolymer (Patent Document 6).
(4) a thermoplastic resin obtainable by adding AES resin and ASA resin to methacrylic ester resin as a hard resin (Patent Document 7).
When using the thermoplastic resin composition of (1) as above, although the scratch resistance is improved against scratches due to enhancing hardness of the surface of the molded article, impact resistance of the molded article is deteriorated due to the low amount of the rubber polymer.
Therefore, there is a limitation in order to satisfy both of impact resistance and scratch resistance of the molded article.
In the thermoplastic resin composition of (2) or (3) as above, it is necessary to add a large amount of an AES resin in order to improve the impact resistance of the molded article. In the resulting molded article, surface hardness (scratch resistance) derived from the methacrylic ester resin and heat resistance derived from maleimide-based copolymer are seriously deteriorated.
Also, since it is necessary to add an AES resin having a large particle size in order to improve impact resistance of the molded article, in the resulting molded article, coloration derived from a hard resin is deteriorated.
In the thermoplastic resin composition of (4) as above, although AES resins and ASA resins are blended in order to suppress deterioration of coloration of the molded article, impact resistance of the molded article is deteriorated as compared to the molded article to which AES resin is blended alone.
A rubber-reinforced resin material typified by ABS resin as a resin material having excellent balance of impact resistance, mechanical properties of the molded article, and fluidity during molding, has been widely used in various fields such as OA equipments, automobiles, miscellaneous goods and the like.
However, since the ABS resin is a non-crystalline (amorphous) resin, the friction coefficient (dynamic friction coefficient, amplitude of the dynamic friction coefficient) of the molded article is large as compared to the polyethylene, polypropylene, or polyacetal as a crystalline resin.
Therefore, since the vibration of the device and the vibration at the start or during running of the automobile cause the stick-slip phenomenon at the switch portion of OA equipment or the connection part of car audio, there is a problem that squeak noise is generated.
As the rubber-reinforced resin material capable of providing a molded article having small the friction coefficient (dynamic friction coefficient, amplitude of the dynamic friction coefficient), the following thermoplastic resin composition have been proposed.
(5) a thermoplastic resin obtainable by adding a polyorganosiloxane as a lubricant to a rubber-reinforced styrene resin (Patent Document 8).
(6) a thermoplastic resin obtainable by adding a silicone resin having a specific viscosity as a lubricant to a rubber-reinforced acrylonitrile-styrene resin containing ABS resin and AES resin (Patent Document 9).
(7) a thermoplastic resin obtainable by adding polytetrafluoroethylene, a low molecular weight oxidized polyethylene or an ultra-high molecular weight polyethylene as a lubricant to a rubber-reinforced styrene resin, an olefin resin and styrene-butadiene-styrene block copolymer (Patent Document 10).
In the molded article obtainable by using the thermoplastic resin compositions of (5) to (7), the lubricant that is added to the thermoplastic resin composition bleeds out on the surface of the molded article, to increase the lubricant property of the molded article, and therefore, the friction coefficient can be reduced.
However, there is a problem in that the bleed-out of the lubricant deteriorates the surface appearance of the molded article, and lubricant property is deteriorated while the lubricant is gradually decreased over time due to bleed-out.